Innate immunity is the first line of defense designed to protect the host from invading pathogens, including HIV. LIR investigators have previously demonstrated that natural killer (NK) cells, an important component of the innate immune response, produced a significant quantity of CC-chemokines that are known to suppress HIV replication through a non-cytolytic mechanism. However, NK cells may control HIV infection through cytolytic mechanisms as well. LIR investigators have analyzed the ability of NK cells to suppress HIV replication from CD4+ T cells of HIV-infected individuals in vitro. Preliminary data suggest that the NK-mediated suppression can be potent and that it is related to the stage of HIV infection as well as the level of HIV plasma viremia. Future studies will focus on elucidating the mechanisms of the suppression of HIV replication by NK cells and the effect of plasma viremia on the function of NK cells